Jersey fits great and has excellent venting breathing. Normally I wear a size small, ordered the SM size and it fits like a fitted small, might be too tight for a true medium. Collar is a bit snug, but just right for a thin guy like myself, those with thicker necks may find it uncomfortable when fully zipped. Sleeves felt a tiny bit longer than normal race fit jerseys but hardly noticeable. Sleeve material is solid (as opposed to meshperforated) but heat didn't seem to be a factor.
Overall I would buy again, if discounted because the actual MSRP is way out of my league.